Beneficiated talcs

ABSTRACT

Means are disclosed for rendering talcs such as Chinese talcs, Australian talcs, Italian talcs or like talcs which, when ground to an approximately 2.5-5.0 μm median particle size, exhibit a wet powder brightness of at least about 30% and which have hitherto been considered acceptable as fillers for thermoplastic resinous compositions, and particularly polypropylene molding resins, even suitable for this use. Such talcs are beneficiated in accordance with this invention, generally at low cost, to further enhance brightness, heat stability or both these properties in thermoplastic molded articles filled with these beneficiated acceptable talcs, while also improving or at least not unacceptably diminishing other significant physical properties, particularly tensile properties, of the resulting molded article. This is accomplished by admixing the Chinese, Australian or Italian talc, or the like, with an effective amount of a combination of: 
     (A) one or a mixture of certain octyl- or nonylphenol/poly(ethylene oxide) condensates, and 
     (B) one or a mixture of certain poly(ethylene glycols) or alkoxypoly(ethylene glycols).

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 003,242, filed Jan. 14, 1987 of common assignmentwith this application.

FIELD OF THE INVENTION

This invention relates to novel, improved, beneficiated talcs. Moreparticularly, this invention relates to means for further improving theperformance characteristics of talcs hitherto considered suitable asfillers for thermoplastic resinous compositions, and to the resultingfurther improved talcs themselves. This invention also relates tothermoplastic resinous compositions filled with talcs which have beenimproved in accordance with the invention and to articles moldedtherefrom whose physical properties, particularly brighness or oven life(long-term heat stability), and preferably both of these properties, arealso improved in comparison to those exhibited by molded articles filledwith the corresponding unbeneficiated talcs.

BACKGROUND OF THE INVENTION

Talc is a relatively abundant, inexpensive, highly water-insoluble,hydrophobic and generally unreactive mineral. It can be categorized as ahydroxylated magnesium silicate and represented by, inter alia, one ormore of the formulas: PG,3

    (Si.sub.2 O.sub.5).sub.2 Mg.sub.3 (OH).sub.2,

    Si.sub.8 Mg.sub.6 O.sub.20 (OH).sub.4, or

    Mg.sub.12 Si.sub.16 O.sub.40 (OH).sub.8,

disregarding impurities, which can include inorganics such ascarbonates, other magnesium silicates, ferrous iron compounds andvarious organic materials. Such impurities generally occur in minuteamounts, but can occur in major amounts as well; certain talcs, forexample, can contain major amounts of dolomite or tremolite. Theimpurities found in talcs will vary as to type and amount depending onthe geographic source of the talc. Even in minute amounts, however,impurities may exert a significant influence on a talc's in-useperformance as a filler for thermoplastic molded articles.

Talc, being naturally organophilic, is highly compatible with and iseasily wet by organic resins. Thus, it has come into widespread use as afiller in thermoplastic resinous compositions, including thosecontaining polyolefins such as polyethylene, polypropylene and the like.Because of talc's thin platelet structure when finely ground, it isconsidered a reinforcing filler rather than an extender. Non-platyparticulate mineral fillers such as calcium carbonate, on the otherhand, are primarily extenders rather than reinforcing fillers.Polypropylene reinforced with talc, in particular, is widely used inappliance applications, where the color of the filled, molded resin is amajor concern, and in automotive applications, especially under-the-hoodautomotive applications, where color is not a particular concern butincreased stiffness, dimensional stability and resistance to heatdistortion are of primary importance. Plastics producers prefer a talcfiller which does not discolor at typical molding temperatures,particularly where the product will be decorative in nature, and whichaffords adequate impact strength and other tensile properties, andadequate long-term heat stability, to the molded plastic.

Two characteristics of a talc--its particle size distribution and itscrude ore source--have been said to affect the properties of talc-filledpolypropylene molded articles. Tests have shown that talc particle sizedistribution affects the stiffness or flexural modulus and tensile yieldof a polypropylene molded article, with tensile yield being mostaffected when the talc filler's cumulative means particle size is lessthan 7 μm. Flexural modulus, on the other hand, has been shown to varyinversely with talc particle size. To further complicate the picture ithas also been found that better long-term heat stability is generallyrealized with increased talc particle sizes; see Bragg et al, PlasticsEngineerging, Vol. 30, No. 9, pp. 30-32 (September 1974).

The apparent particle size distribution in talc from any geographicsource, as measured by typical gravimetric particle size distributionmethods, can be made comparable to that of talc from any other source bygrinding. However, matching the aspect ratio of talc from one geographicsource by grinding talc from another geographic source which has adifferent aspect ratio cannot easily be accomplished. Geographic sourceitself--or more particularly the different kinds and amounts ofimpurities present in talcs from different geographic sources--raisesanother problem which is not so easily solved. Talcs from certaingeographic sources, such as Montana talcs (Yellowstone and Beaverheadtalcs, for example), have been found to be inferior to those from othersources, particularly California, as fillers for polypropylene. Bragg etal have shown, for example, that Montana talc-filled polypropylene ispoorer in heat stability than California talc-filled polypropylene whentreated at 365° F. for 16 hours, no matter when the particle size,coarse or fine, of the talc used, and that to obtain equal long-termheat aging performance, a higher overall heat stabilizer level must beused in Montana talc-filled polypropylene than in California talc-filledpolypropylene.

A comparison of the chemical composition of theoretical and typicalcommercial talcs is given in Radosta, Plastics Compounding,September/October 1979, pp. 24, 26-28 and 30, at page 24 (Table I):

    ______________________________________                                               Theoretical                                                                           Montana   California                                                                              Vermont                                           pure talc                                                                             talc      talc      talc                                       ______________________________________                                        SiO.sub.2 %                                                                            63.5      62.5      57.4    56.2                                     MgO, %   31.7      30.6      27.6    30.8                                     CaO, %             0.3       6.2     0.4                                      Al.sub.2 O.sub.3, %                                                                    0.5       1.4       0.5                                              Fe.sub.2 O.sub.3, %                                                                              0.7       0.3     3.9                                      Loss on  4.8       5.4       7.1     8.2                                      ignition, %                                                                   ______________________________________                                    

Mathur et al, in Society of Plastics Engineers Technical Papers, Vol.25, pp. 663-667 (1979) reported on their studies of the deterioration ofoven aging characteristics in heat-stabilized polypropylene moldingsfilled with certain high aspect ratio talcs. These authors found that"(t)he melt compounding of Montana talcs as well as Vermont talcsresults in significant discoloration of molded parts, while Californiatalcs do not discolor the matrix." No loss of mechanical properties,however, was seen to be associated with this discoloration. Mathur et alalso found that while "(t)he primary source for polypropylene colorationby Montana and Vermont talcs is not well understood, . . . it can beminimized by the use of . . . processing aids, such as calcium stearate,carbowax and amide processing lubricants."

U.S. Pat. No. 3,553,158, issued Jan. 5, 1971 to Gilfillan and mentionedin the Mathur et al article, discloses heat-stabilized, talc-filledpolypropylene molding resin compositions containing a "talcdeactivating" organic polar compound, preferably an epoxide(particularly a polyepoxide), an amide, an acrylate polymer or analiphatic polyol. According to Gilfillan, such compounds generally

". . . Will have a molecular weight greater than about 300; will containone or more polar groups such as epoxide, aliphatic hydroxyl, ester,amide, ether or sulfide; and will preferably contain a non-polar organicgroup which makes them at least moderately compatible with the polymer,such as lauryl or stearyl";

see column 7, lines 41-58 in the Gilfillan patent. Carbowax 400 andCarbowax 6000 are sspecifically disclosed as "talc deactivating"compounds in Gilfillan's Table I, the talcs treated in the workingexamples were Montana talcs, and calcium stearate was included in thecompositions of at least working examples 1-3.

Shimizu et al, in Japanese Kokai 75 8, 098, published Apr. 2, 1975[Chem. Abst. 83: 98595j (1975)] disclose increasing the discolorationresistance of polypropylene homopolymer and copolymer moldingcompositions containing talc by adding thereto, as a "reforming agent",a polyalkylene glycol alkyl ether or polyalkylene glycol alkylphenylether such as a "polyalkylene glycol phenoxyether", polyethylene glycoloctylphenyl ether, polyethylene glycol lauryl ether or polyethyleneglycol/polypropylene glycol ether.

Other publications which disclose treating talc or talc-containingthermoplastic resinous compositions to improve the properties ofthermoplastic resinous molded articles made from them include thefollowing:

U.S. Pat. No. 4,115,897, issued Sept. 26, 1978 to Huszar et al, whichdiscloses polyolefin molding compositions containing talc and a mixtureof two surfactants--one of which can be alkylphenyl polyether--havingdifferent HLB values; see column 3, lines 1-17 and 67 and column 4, line17.

Talc filler coated with at least one metallic salt of an 8-20 carbonatom-containing fatty acid, e.g., calcium stearate, is disclosed in U.S.Pat. No. 4,255,303, issued Mar. 10, 1981 to Keogh; see column 4, lines13-32.

Mineral fillers such as talc coated with a thin layer of liquid ethyleneoxide oligomer having a molecular weight of from 100-800 are shown inU.S. Pat. No. 4,411,704, issued Oct. 25, 1983 to Galeski et al; seecolumn 2, lines 11-20 and 23.

Transparent polypropylene food packaging materials which are easilyincinerated after use and which contain talc, a polyol ester suchaspolyethylene glycol monostearate or glycerol distearate, andantioxidants and stabilizers, included among which is epoxidized soybeanoil, are shown in Tsunetsugu et al Japanese Kokai 75 109,239, publishedAug. 28, 1975 [Chem. Abst. 83: 207145k (1975)].

Rusznak et al, Muanvag Gumi, Vol. 16, No. 9, pp. 257-261 [Hung. 1979;Chem. Abst. 92: 42775m (1980)] discloses isotactic polypropylenecompositions containing talc, a surfactant and an "elastomeric adhesionimprover".

Talc-filled polypropylene molding compositions containing oleic amide asa processing aid together with BHT (butylated hydroxytoluene, anantioxidant) are taught in Tokuyama Soda's Japanese Kokai 80 142,039,published Nov. 6, 1980 [Chem. Abst. 94: 122583d (1981)].

The treatment of talc with solid resins, such as hydrogenated petroleumresin, wax (e.g., stearic acid) or a combination of such substances toimprove the talc's compatibility with polyolefins is shown in Matsumotoet al Japanese Kokai 78 65,346, published June 10, 1978 [Chem. Abst. 89:147656q (1978)].

Goel et al, Polym. Eng. Sci., Vol. 20, No. 3, pp. 198-201 (1980) [Chem.Abst. 92: 129772g (1980)], disclose adding small amounts of oligomericpolypropylene oxide to talc-filled isotactic polypropylene to decreaseboth viscosity and elasticity.

A 1978 Research Disclosure, Vol. 173, No. 19 [Chem. Abst. 89: 180758x(1978)] teaches that low melting cellulose acetate butyrate is a goodheat stabilizer for talc-filled polypropylene.

Copending U.S. patent application Ser. No. 003,242 relates to thediscovery that Montana talc and like talcs regarded, in theunbeneficated state, as inferior fillers for thermoplastic resinouscompositions, and particularly polypropylene molding resins, becausethey discolor the resinous matrix when subjected to typical moldingconditions and adversely affect its long-term heat stability, can berendered suitable for this use, at low cost, by treatment with novelcombinations of particular amounts of certain materials. Thermoplasticresinous molded articles containing the thus-treated talcs have beenfound to exhibit significantly reduced darkening (as measured by theGeneral Electric brightness test), without unacceptably increasedyellowing (as measured by the Hunterlab yellowness index), and improvedheat stability (as measured by oven aging) when compared to moldedarticles containing the corresponding untreated, inferior talc.

Talcs such as certain Chinese, Australian and Italian talcs, in contrastto Montana talc and like talcs, are acceptable fillers for thermoplasticresinous compositions such as polypropylene molding resins, and givemolding resins which do not discolor when molded and ordinarily exhibitno unacceptable diminution in long-term heat stability as compared tothe unfilled resin. It has now been discovered, however, that one orboth of the brightness and heat stability of thermoplastic moldedarticles filled with such acceptable talcs can be unexpectedly enhanced,while maintaining acceptably comparable tensile properties (flexuralmodulus, Gardner impact strength, Izod impact strength and heatdeflection temperature), by treating those of such acceptable talcswhich, when ground to an approximately 2.5-5.0 μm median particle size,exhibit a wet powder brightness (GE brightness or "GEB") of at leastabout 30%, with the novel beneficiating compositions disclosed incopending application Ser. No. 003,242.

It is, therefore, an object of this invention to provide novel,improved, beneficiated talcs.

A further object of this invention is to provide thermoplastic resinouscompositions filled with novel, improved, beneficiated talcs.

Another object of this invention is to provide beneficiated acceptabletalcs which, when incorporated as fillers in thermoplastic moldedarticles, result in such articles exhibiting enhanced brightness, heatstability, or both, as compared to articles molded from compositionscontaining the corresponding unbeneficiated talc as filler, whilemaintaining acceptably comparable tensile properties.

These and other objects, as well as the nature, scope and utilization ofthis invention, will become readily apparent to those skilled in the artfrom the following description and the appended claims.

SUMMARY OF THE INVENTION

It has now been discovered that an effective amount of a combination of:

(A) one or a mixture of octyl-or nonylphenol/poly(ethylene oxide)condensates, and

(B) one or a mixture of poly(ethylene glycols) or alkoxypoly (ethyleneglycols),

can be applied to a talc which, in its unbeneficiated state, is anacceptable filler for thermoplastic resinous compositions and which,when ground to an approximately 2.5-5.0 μm median particle size,exhibits a wet powder brightness (determined according to the proceduredescribed hereinbelow) of at least about 30%. Such talcs include Chinesetalcs, Australian talcs, including cosmetic grade Autralian talcs,Italian talcs, and like talcs. This beneficiating combination willfurther enhance the brightness, heat stability or both of thermoplasticmolded articles, such as polypropylene molded articles, filled with suchbeneficiated talcs, while maintaining tensile properties acceptablycomparable to those found in articles molded from thermoplastic resinouscompositions filled with the corresponding unbeneficiated talcs.

Such additive combinations do not cause unpleasant odors in talc-filledmolding resins containing them. These additive combinations are also ofa relatively low order of toxicity, and hence do not prevent thebeneficiated talc-containing resinous compositions of this inventionfrom being used to prepare molded articles which can come in contactwith foods, e.g. microwave oven and refrigerator liners.

DETAILED DESCRIPTION OF THE INVENTION

The octyl- or nonylphenol/poly(ethylene oxide) condensates employed inpracticing this invention can be represented by the general formula:##STR1## wherein R represents one or a mixture of C₈ or C₉ alkyl groups,preferably branched-chain isomers such as an isooctyl group, ##STR2##and x is a number of from about 3to about 40, indicating the averagenumber of ethylene oxide units in the ether side chain. Members of theoctylphenol and nonylphenol series of nonionic surfactants sold by Rohmand Haas Company under the trademark Triton can be used in practicingthis invention, and Triton X-114 surfactant, anoctylphenol/poly(ethylene oxide) condensate having, an average, 7-8ethylene oxide units in the ether side chain, is particularly preferred.

The poly(ethylene glycols) and alkoxypoly(ethylene glycols) which can beused in practicing the present invention can be represented by thegeneral formula: ##STR3## wherein R' represents hydrogen or a loweralkyl group having from 1-4 carbon atoms, inclusive, preferably methylor ethyl, and y is a number such that the average molecular weight ofthe poly(ethylene glycol) or alkoxypoly(ethylene glycol) is from about100 to about 20,000, and preferably from about 200 to about 14,000.

Members of the series of poly(ethylene glycols) and alkoxypoly(ethyleneglycols) sold by Union Carbide Corporation under the trademark Carbowaxcan be used in practicing this invention; Carbowax polyethylene glycol200 (y=about 4) and Carbowax polyethylene glycol 300 (y=about 6) whichare liquids at room temperature, are particularly preferred. Highermolecular weight solid members of this series can, of course, be used,but are somwheat more difficult to work with.

Ordinarily, in practicing this invention a Chinese, Australian, Italianor like talc having incorporated therewith an effective, beneficiatingamount of a combination of one or a mixture of the octyl- ornonylphenol/poly(ethylene oxide) condensates and one or a mixture of thepoly(ethylene glycols) or alkoxypoly(ethylene glycols) will be used as areinforcing filler in articles molded from commercially available,heat-stabilized thermoplastic, e.g., polypropylene, resins. The amountof such combinations of beneficiating additives employed will besufficient to beneficiate or upgrade the in-use performance of a talcalthough acceptable as a filler which, prior to beneficiation, does notfurnish the property levels set out immediately hereinbelow.

As indicated above, one measure of acceptability as a filler is a wetpowder brightness (GEB) of at least about 30% exhibited by a talc whichhas been found to an approximately 2.5-5.0 μm median particle size.Representative talcs for which wet powder brightness has been determinedin the manner described hereinbelow are:

    ______________________________________                                                     Median Particle                                                                            Wet Powder                                          Talc         Size (μm) Brightness (GEB. %)                                 ______________________________________                                        Mistron 400 Mon-                                                                           4.5          20.2                                                tana Yellowstone                                                              Mistron PV Chinese                                                                         2.6          46.8                                                No. 6 Hegman Aust-                                                                         2.9          41.7                                                ralian Cosmetic Grade                                                         Suprafino Italian                                                                          5.0          33.6                                                ______________________________________                                    

Beneficiation in the manner taught by this invention will upgrade aChinese, Australian, Italian or like talc's performance to the point atwhich the molded article, at 40 weight percent filler loading in Amoco1046 polypropylene resin, exhibits improvement in at least one andpreferably both of brightness (GE brightness, measured in the mannerdescribed below or in an equivalent manner) and oven life upon aging at155° C., and in fact brightness will usually be improved, together withimprovement or at least no unacceptable diminution in other significantphysical properties, particularly flexural modulus and impact strength.In general, such a molded article will exhibit a GE brightness of atleast about 30% and withstand oven aging at 155° C. in an atmosphere ofair for at least 10 days. Its flexural modulus will be at least about440 ksi, its Gardner impact strength will be at least about 8.0f.-lbs./in., its notched Izod impact strength will be at least about0.45 ft./lb. in notch, and its heat deflection t4emperature will be atleast 160° F. at 264 psi.

An effective amount of a beneficiating composition of this inventionwhich will provide the aforementioned levels of property improvement,and particularly acceptable brightness, acceptable oven life at 155° C.,or both to a thermoplastic, e.g., polypropylene molded article filledwith a Chinese, Australian, Italian or like talc usually will range fromabout 0.05% to about 4.0% by weight, and preferably from about 0.2% toabout 1.50% by weight, of one or a mixture of the octyl- ornonylphenol/poly(ethylene oxide) condensates, and from about 0.05% toabout 4.0% by weight, and preferably from about 0.2% to about 1.50% byweight, of one or a mixture of the poly(ethylene glycols) oralkoxypoly(ethylene glycols). The total amount of octyl- ornonylpheol/poly(ethylene oxide (condensate(s) and poly[ethyleneglycol(s)] or alkoxypoly [ethylene (glycols)] combined ordinarily willbe no more than about 5.0% by weight, and preferably no more than about3% by weight. The aforementioned weight percents are each based on theweight of the unbeneficiated talc being treated.

These beneficiating materials can be mixed with the talc before addingit to the remaining ingredients of themolding composition, and indeedbefore grinding the talc, if desired, or they can be mixed with theseingredients and the talc in any other desired order, either before orwhile talc is compounded with the remaining components of the moldingresin composition (e.g., they can be added to the blender or to the meltin an extruder from which molding resin pellets are obtained). Whenthese materials are mixed with the talc itself, they may be added to thetalc directly or first dissolved in a suitable organic solvent,preferably a polar solvent such as a lower alkanol, e.g., ethanol orisopropanol, a ketone such as acetone, methyl ethyl ketone or methylisobutyl ketone, a low molecular weight Cellosolve, e.g.,2-butoxyethanol, and the like, or mixtures thereof, then added to thetalc, e.g., by spraying or wet blending, and the solvent evaporated.

Treated talcs can be prepared in a Henschel or similar blender or thelike which can used to mix and blend the ingredients tomacrohomogeniety, i.e., to less than complete uniformity, particularlywhen a relatively small sample is considered, or to greater uniformityof desired, at any temperature up to the decomposition point of the mosteasily decomposable component. The treated talcs can be compounded withthe resin using a Leistritz compounder-extruder or other suitabledevice.

Molding compositions containing the treated talcs of this invention,particularly, those compositions used to provide molded articles intenedfor use in elevated temperature environments, can also containconventionally-employed types and amounts of other additives: primaryantioxidants (heat-stabilizers) including hindered phenols such as:

1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6,(1H,3H,5H)-trione,

1,3,5-trimethyl-2,4,6-tris[3,5-di-ter-butyl-4-hydroxybenzyl]benzene,

2,6-di-tert-butyl-4-methylphenol,tetrakis[methylene(3,5-di-tert-butyl-4-hydroxycinnamate)]methane,

N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide),

O,O-di-n-octadecyl-3,5-di-tert-butyl-4-hydroxy benzyl phosphonate,

2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,2,5-triazine,

thiodiethylenebis(3,5,-tert-butyl-4 hydroxy)hydrocinnamate, octadecyl3,5-di-tert-butyl-4-hydroxyhydrocinnamate,

tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,

1,1,3,-tris(5-tert-butyl-1,4-hydroxy-2-methylphenyl)butane,

and the like, esters such asoctadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,pentaerythritol tetra-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],and the like, secondary stabilizers, e.g., dialkylthiodipropionates suchas distearylthiodipropionate, dilaurylthiodipropionate, epoxides, andthe like, extendeers such as calcium carbonate, pigments, e.g., carbonblack and titanium dioxide, dyes, mold lubricants, e.g., calciumstearate, other reinforcing agents, e.g. fibrous reinforcing agents suchas glass fiber, carbon or carbon/graphite fibers, and the like.

Besides polypropylene molding resins, any other thermoplastic materialsfillable with talc or other reinforcing fillers, including otherpolyolefin polymers, such as homopolymers, copolymers and blendscontaining them, polyesters such as polyethylene terephthalate,poly(1,4-butanediol)terephthalate, and the like, all-aromaticpolyesters, e.g., aromatic diacid/aromatic diol/±hydroxy aromatic acidcopolymers, polycarbonates, polyoxymethylene homo- and copolymers, e.g.,acid anhydride end-capped oxymethylene homopolymers andtrioxane/ethylene oxide copolymers, ABS, SBR, EPDM and neoprene rubbers,polyisoprene, and the like can be filled with the benficiated talcs ofthis invention, using art-recognized techniques.

The beneficiated talcs of the present invention can be used as fillersin thermoplstic resinous compositions in the amounts in which talc hashitherto been used for this purpose. Typical filler loadings can rangefrom about 10% to about 50% by weight, and preferably from about 15% toabout 30% by weight, or from about 35% to about 50% by weight, based onthe total weight of the filled composition. Amounts of the beneficiatedtalcs of this invention within these ranges will be used, for example,when polypropylene is the resin being filled.

In order that those skilled in the art can more fully understand thisinvention, the following examples are set forth. These examples aregiven solely for purposes of illustration, and should not be consideredas expressing limitations unless so set forth in the appended claims.All parts and percentages are by weight, unless otherwise stated.

EXAMPLES 1 AND 2

A single batch of Mistron PV Chinese talc (Cyprus Industrial MineralsCompany) having a median particle size of approximately 2.6 μm and aparticle size distribution such that 80% of the particles are finer thanabout 4.5 μm and 20% of them are finer than about 0.75 μm was used forboth of these examples. In all cases when describing particle size interms of the percent of particles finer than a specified diameter, theword "particles" actually refers to the total mass of all particles inthe sample whose diameters are smaller than the specified value.Similarly, the median particle size is defined as the particularparticle diameter where exactly one-half the total mass of the sample iscomposed of particles having lesser diameters.

In Example 1 a sample of talc treated with the amount and type ofadditives listed in Table 1 below was mixed with Amoco 1046polypropylene, an antioxidant-containing resin, at a temperature rangingfrom 325°-430° F. in a Leistritz compounder-extruder. In Example 2, noadditives were used on the talc.

In each case, a filled resin batch having a talc content of 40%, basedon the total weight of the batch, was prepared. Each such batch was thenused to prepare, by melting at a temperature of 360°-435° F., using anArburg injection molding machine, and then injecting into a 140° F.steel mold and holding under pressure for 56 seconds, sufficientquantities of discs and tensile bars conforming to ASTM and otherapplicable standards to permit testing according to ASTM standards,variations thereof, and other test methods as described hereinbelow.

The following tests were performed on these molded discs or bars fromeach talc sample:

1. Oven Aging--a procedure used to evaluate the relative thermalstabilities of the injection molded polypropylene specimens.

One tensile bar and one disc of each material tested were placed on thestainless steel grills of a force-air circulation oven (Despatch OvenCompany; Ser. No. 9376-3L) at 155° C. (measured by the oven's outsideindicator and a temperature dial gauge placed inside the oven) and thestarting time (day and time specimens were placed in the oven) wasnoted. The oven grils were shifted once daily (except on weekends) in apattern which insured uniform air exposure.

The specimens were inspected once a day (execpt on weekends), and aspecimen was considered to have failed when approximately 10% of itssurface showed "crazing" (surface cracks or deterioration),embrittlement or serious discoloration. The oven temperature asindicated inside and outside the oven was recorded at this time, as wasthe inspection time (in clock hours from the start of the test) and anyobserved failures. The oven life of a sample was expressed in days tofailure.

2. GE Brightness (GEB)--a procedure used to determine the brightness ofthe injection molded polypropylene specimens.

A minimum of three (and preferably five) specimen discs were evaluatedfor each material tested. After first making certain that the filterwheel of a Technidyne brightimeter, Model S-4, was in position 1 andcentered, the instrument was turned on and its calibration checked byplacing an opal glass standard block over the sample opening and thenadjusting the "Cal Adjust" knobs on the front of the instrument so thatthe instrument read the brightness value indicated on the standard. Thecalibration was rechecked in this fashion every few minutes while theinstrument was in actual use.

A specimen disk was then set over the sample opening and a 1 kg brassweight placed on top of the sample. The digital panel meter settled on areading in 1-2 seconds:

if the last digit of this reading oscillated between two numbers, theone which predominated was chosen;

if neither number predominated, the lower digit was chosen.

The instrument's "Enter" knob was then pressed to print the reading bymeans of a Canon printer, Model cp 1002.

This procedure was then repeated:

to obtain readings from three different surface spots on each disc;

to obtain readings for 3-5 discs representing each material tested.

After each 9-15 readings, the "Average" knob was pressed to obtain theaverage of the readings for each sample.

The procedure for determining Wet Powder Brightness, i.e., thebrightness of unbeneficiated talc, is carried out as follows:

Six grams of paraffin wax flakes (Kodak, granular) and four grams of thetalc being tested (2.5-5.0 μm median particle size) are mixed in anapproximately 2 inch diameter aluminum tart pan. The pan is placed on ahot plate (approximately 280° F. plate surface temperature) and theparaffin melted completely. After stirring to give a uniform mixture andthen allowing the mixture to cool, the sample is removed from the panand tested for brightness/color using a suitable instrument, e.g., theaforementioned Technidyne brightimeter or a Hunterlab colorimeter.

3. Flexural Modulus--ASTM D-790.

4. Gardner Impact Test--a procedure for determining the energy requiredfor a falling weight applied under specified conditions to crak or breakthe injection molded polypropylene specimens.

A minimum of twenty specimen discs, allowed to age under ambient labconditions for a minimum of 7 days before testing, were impacted foreach material tested. Next, using a micrometer, the average nominalthickness of these discs was determined.

A specimen disc was then positioned, with the knockout pin marks facingup, over the support anvil of a Gardner Laboratories Model IG-1120Variable Height Impact Tester having cylindrical 2, 4 and 8 lb. weightswhich can be dropped through a vertical guide tube for distances of upto about 1 meter (40 inches). The tip of the instrument's impactor waspositioned to rest at the center point on the disc.

A 2 lb. weight was raised to the desired height and released. Thisallowed the weight to fall freely and strike the impact plunger. Afterimpact, the disc was removed and the impacted area visually inspectedfor failure. Failure is defined as any of the following conditions:

the disc was broken to pieces;

the center area protruded on the disc surface opposite the one havingthe knockout pin marks;

if neither of these conditions obtained, the disc was bent by hand andthen visually reexamined for cracks on the surface opposite the onehaving the knockout pin marks; if cracks occurred, and the depth of anyone of them was more than one-third the thickness of the disc, this wasconsidered a failure.

The starting point for the staircase (up and down) method was determinedon several impacts by halving or doubling the drop height until apass-fail point was determined. The next specimen was impacted using thedrop height corresponding to the pass-fail point determined in thismanner. If the specimen pass, the next specimen was tested at a dropheight one inch higher. If the specimen failed, the next specimen wasimpacted at a drop height one inch lower. This procedure was continueduntil twenty specimens were tested, with a running record being kept offailures and non-failures.

    ______________________________________                                        Calculations                                                                  ______________________________________                                        h     =     h.sub.o + d(A/N) ± 0.5D                                        Where:                                                                        h     =     mean failure height, in.                                          d     =     increment of height, in (=1 in.)                                  N     =     total number of failures or non-failures                                      (events), whichever was smaller. If they were                                 equal, failures were used.                                        h.sub.o                                                                             =     lowest height at which an event ocurred, in.                       A     =                                                                                   ##STR4##                                                         i     =     0,1,2, . . . K (counting index, 0 starts at h.sub.o)              n.sub.i                                                                             =     number of events occurring at h.sub.i                             h.sub.i                                                                             =     h.sub.o + id                                                      h.sub.k                                                                             =     largest height at which an event occurred, in.                    ±  =     for failures -- was used; for non-failures + was used.            MFE   =     hWf                                                               Where:                                                                        MFE   =     mean failure energy (50% failure),                                            joules or inch-pounds                                             h     =     mean failure height, in.                                          W     =     weight, lb.                                                       f     =     factor for conversion to joules                                         =     1.0 to get US units (in.-lbs.) if h = in. and W = lbs.             S     =                                                                                   ##STR5##                                                         Where:                                                                        S     =     estimated standard deviation                                       B     =                                                                                   ##STR6##                                                         5. Heat Deflection Temperatures - ASTM D-648 (264 psi).                       6. Izod Impact Strength - ASTM D-256.                                         ______________________________________                                    

The results of these tests are set out in Table I below. In this and allsubsequent tables the notation "wt.%" in the "Additive(s)" columns is aclose approximation of actual weight percents used. The actual additiveadditions were made based on parts of additive(s) added per hundredparts of talc filler.

                                      TABLE I                                     __________________________________________________________________________                           GE        Gardner                                                                             Heat Def-                                                Oven Bright-                                                                           Flexural                                                                            Impact                                                                              lection Izod Impact                    Example                                                                            Additives    Aging.sup.(1)                                                                      ness.sup.(2)                                                                      Modulus.sup.(3)                                                                     Strength.sup.(4)                                                                    Temperature.sup.(5)                                                                   Strength.sup.(6)               __________________________________________________________________________    1    1.12 wt. % Triton X-114                                                                    20   43.11                                                                             607   12.5  192     0.51                                0.38 wt. % Carbowax 300                                                  2    None         11   31.73                                                                             625   7.8   179     0.52                           __________________________________________________________________________     .sup.(1) Days to failure; fdw = failed during weekend, hence, number of       days to failure given may be one or two less than recorded.                   .sup.(2) Percent.                                                             .sup.(3) 10.sup.3 psi.                                                        .sup.(4) In ft. lb./in. of thickness                                          .sup.(5) In °F. at 264 psi fiber stress.                               .sup.(6) In ft. lb./in. of notch.                                        

EXAMPLES 3 AND 4

The procedure of Examples 1 and 2 was repeated in every essential detailbut one, namely, the talc used in Examples 3 and 4 was from a singlebath of Mistron P-1 Chinese talc (Cyprus Industrial Minerals Company)having a median particle size of approximately 3.7 μm and a particlesize distribution such that 80% of the particles are finer than about6.3 μm and 20% of them are finer than about 1.6 μm. In Example 3 thetalc was additive-treated; in Example 4 no beneficiating additives wereused.

The results of the tests performed on molded specimens of thethus-obtained molding resins are given in Table II below. Notes 1-6, arethe same as for Table I.

                                      TABLE II                                    __________________________________________________________________________                           GE        Gardner                                                                             Heat Def-                                                Oven Bright-                                                                           Flexural                                                                            Impact                                                                              lection Izod Impact                    Example                                                                            Additives    Aging.sup.(1)                                                                      ness.sup.(2)                                                                      Modulus.sup.(3)                                                                     Strength.sup.(4)                                                                    Temperature.sup.(5)                                                                   Strength.sup.(6)               __________________________________________________________________________    3    1.12 wt. % Triton X-114                                                                    20   41.4                                                                              596   10.5  189     0.53                                0.38 wt. % Carbowax 300                                                  4    None         16   30.3                                                                              596   8.1   181     0.53                           __________________________________________________________________________

EXAMPLES 5-12

The procedure of Examples 1 and 2 was again repeated in every essentialdetail except for the following:

the talc used in Examples 5 and 6 was from a single batch of 200 meshAustralian cosmetic grade talc having a median particle size ofapproximately 12 μm and a particle size distribution such that 80% ofthe particles are finer than about 25 μm and 20% of them are finer thanabout 4.3 μm;

the talc used in Examples 7 and 8 was from a single batch of 325 meshAustralian cosmetic grade talc having a median particle size ofapproximately 5.4 μm and a particle size distribution such that 80% ofthe particles are finer than about 9.8 μm and 20% of them are finer thanabout 2.4 μm;

the talc used in Examples 9 and 10 was from a single batch of No. 5Hegman Australian cosmetic grade talc having a median particle size ofapproximately 2.7 μm and a particle size distribution such that 80% ofthe particles are finer than about 4.6 μm and 20% of them are finer thanabout 1.1 μm;

the talc used in Examples 11 and 12 was from a single batch of No. 6Hegman australian cosmetic grade talc having a median particle size ofapproximately 2.9 μm and a particle size distribution such that 80% ofthe particles are finer than about 4.9 μm and 20% of them are finer thanabout 1.3 μm;

In Examples 5, 7, 9 and 11 the talc was additive treated; in Examples 6,8, 10 and 12 no beneficiating additives were used.

The results of the tests performed on molded specimens of thethus-obtained molding resins are given in Table III below. Notes 1-6 arethe same as for Table I.

                                      TABLE III                                   __________________________________________________________________________                           GE        Gardner                                                                             Heat Def-                                                Oven Bright-                                                                           Flexural                                                                            Impact                                                                              lection Izod Impact                    Example                                                                            Additives    Aging.sup.(1)                                                                      ness.sup.(2)                                                                      Modulus.sup.(3)                                                                     Strength.sup.(4)                                                                    Temperature.sup.(5)                                                                   Strength.sup.(6)               __________________________________________________________________________    5    0.88 wt. % Triton X-114                                                                    21   30.0                                                                              445   10.9  163     0.48                                0.30 wt. % Carbowax 300                                                  6    None         16   19.3                                                                              499   11.6  167     0.53                           7    0.88 wt. % Triton X-114                                                                    17   33.4                                                                              524   8.6   172     0.51                                0.30 wt. % Carbowax 300                                                                    (f.d.w.)                                                    8    None         13   22.1                                                                              605   7.9   171     0.54                           9    0.88 wt. % Triton X-114                                                                    13   41.9                                                                              587   8.4   181     0.50                                0.30 wt. % Carbowax 300                                                                    (f.d.w.)                                                    10   None          8   25.8                                                                              664   6.5   190     0.48                           11   0.88 wt. % Triton X-114                                                                    17   40.1                                                                              607   8.5   177     0.53                                0.30 wt. % Carbowax 300                                                  12   None          8   27.6                                                                              671   11.2  173     0.54                           __________________________________________________________________________

EXAMPLES 13 AND 14

The procedure of Examples 1 and 2 above was again repeated in everyessential detail but one, namely, the talc used in Examples 13 and 14was from a single batch of Suprafino Italian talc (Cyprus IndustrialMinerals Company) having a median particle size of approximately 4.9 μmand a particle size distribution such that 80% of the particles arefiner than about 8.9 μm and 20% of them are finer than about 2.2 μm. InExamples 13, the talc was additive treated; in Examples 14 nobeneficiating additives were used.

The results of the tests performed on molded specimens of thethus-obtained molding resins are given in Table IV below. Notes 1-6 arethe same as for Table I.

                                      TABLE IV                                    __________________________________________________________________________                           GE        Gardner                                                                             Heat Def-                                                Oven Bright-                                                                           Flexural                                                                            Impact                                                                              lection Izod Impact                    Example                                                                            Additives    Aging.sup.(1)                                                                      ness.sup.(2)                                                                      Modulus.sup.(3)                                                                     Strength.sup.(4)                                                                    Temperature.sup.(5)                                                                   Strength.sup.(6)               __________________________________________________________________________    13   1.12 wt. % Triton X-114                                                                    13   33.7                                                                              669   8.5   201     0.53                                0.38 wt. % Carbowax 300                                                  14   None         21   27.9                                                                              708   8.1   205     0.52                                             (f.d.w.)                                                    __________________________________________________________________________

The above discussion of this invention is directed primarily topreferred embodiments and practices thereof. It will be readily apparentto those skilled in the art that further changes and modifications inthe actual implementation of the concepts described herein can easily bemade without departing from the spirit and scope of the invention asdefined by the following claims.

I claim:
 1. A beneficiated talc suitable for use as a filler forthermoplastic resinous compositions comprising a talc which, when groundto an approximately 2.5-5.0 μm median particle size, exhibits a wetpowder brightness of at least about 30%, admixed with:(a) one or amixture of otyl- or nonylphenol/poly(ethylene oxide) condensates, and(b) one or a mixture of poly(ethylene glycols) or alkoxypoly(ethyleneglycols), said (a) and said (b) each being present in an amount rangingfrom about 0.05% to about 4.0% by weight, with the total combined amountof said substances being no more than about 5.0% by weight, said weightpercents being based on the weight of the unbeneficiated talc.
 2. Abeneficiated talc as recited in claim 1 in which said (a) is anoctylphenol/poly(ethylene oxide) condensate.
 3. A beneficiated talc asrecited in claim 1 in which said (b) is a poly(ethylene glycol).
 4. Abeneficiated talc as recited in claim 1 in which said (a) is anoctylphenol/poly(ethylene oxide) condensate having an average of 7-8ethylene oxide units in its ether side chain and said (b) is apoly(ethylene glycol) having a molecular weight of from about 200 toabout
 300. 5. A beneficiated talc as recited in caim 1 in which saidtalc is a Chinese talc.
 6. A beneficiated talc as recited in claim 1 inwhich said talc is an Australian talc.
 7. A beneficiated talc as recitedin claim 1 in which said talc is an Italian talc.
 8. A beneficiated talcas recited in any one of claim 1-4, inclusive in which said octyl- ornonylphenol/poly(ethylene oxide) condensate and said poly(ethyleneglycol) or alkoxypoly(ethylene glycol) are each present in an amountranging from about 0.2% to about 1.5% by weight, with the total combinedamount of said substances being no more than about 3.0% by weight, saidweight percents being based on the weight of the unbeneficiated talc. 9.A beneficiated talc as recited in claim 8 in which said talc is aChinese talc.
 10. A beneficiated talc as recited in claim 8 in whichsaid talc is an Australian talc.
 11. A beneficiated talc as recited inclaim 8 in which said talc is an Italian talc.